In a prior form of a device having hydraulic actuators for opening a door on an airplane to expose a refueling receptacle having latches for connecting to a nozzle on a tanker plane for refueling in flight, and wherein such prior device controlled another hydraulic actuator for operating the latches into and out of holding engagement with the nozzle, it has been possible to inadvertently cause closing movement of the door before the latches were disengaged from the nozzle. This is a dangerous situation that could cause damage to the parts and possibly cause hazardous fuel spills. In addition, although such prior device has a spring for opening the door in case of failure of pressure fluid being delivered to the hydraulic actuator for opening the door, fluid pressure developed in hydraulic return lines could prevent the spring from opening the door.
It is an object of this invention to overcome these difficulties with prior devices. It is another object to mount the door opening device on a base so that it can be installed and removed from an airplane as a unit and which unit can be tested outside the airplane, as in a laboratory.